This article compares the efficiency of induced polarization (IP) and resistivity in characterizing a contamination plume due to landfill leakage in a typical tropical environment. The resistivity survey revealed denser electrical current flow that induced lower resistivity values due to the high ionic content. The increased ionic concentration diminished the distance of the ionic charges close to the membrane, causing a decrease in the IP phenomena. In addition, the self-potential (SP) method was used to characterize the preferential flow direction of the area. The SP method proved to be effective at determining the flow direction; it is also fast and economical. In this study, the resistivity results were better correlated with the presence of contamination (lower resistivity) than the IP (lower chargeability) data.
ABSTRACT. Resistivity geophysical techniques were applied closed to the Londrina's county sanitary landfill, allowing the detection and mapping of leachate contamination plume. The study area lies on the Paraná Basin which is locally represented by basaltic rocks of the Serra Geral Formation.A correlation between lower resistivity values and the supposed leachate contaminations was stablished, once the electrical conduction, under natural conditions, occurs mainly in an ionic way, which are normally presented in the leachate.The main contamination flows in a general SE direction. An unexpected finding of this work was the detection of another flux direction of contamination plume to SW, which flows trough horizontal fractures or alteration surfaces of basaltic contacts.Keywords: resistivity, contamination.RESUMO. Ensaios geofísicos de eletrorresistividade foram efetuados junto ao aterro sanitário do Município de Londrina, permitindo a detecção e mapeamento da pluma de contaminação pelo chorume. Aárea de estudo situa-se na Bacia do Paraná, a qual está localmente representada pelas rochas basálticas da Formação Serra Geral.Estabeleceu-se uma correlação entre os valores mais baixos de resistividade e as possíveis contaminações, uma vez que a condução elétrica, em condições naturais, ocorre principalmente através deíons, que são abundantes no chorume.O fluxo da contaminação principal apresenta uma direção geral SE. Uma descoberta inesperada deste trabalho foi a identificação de outra direção do fluxo da pluma de contaminação para SW, a qual flui através de fraturas horizontais ou superfícies de alteração em contatos dos derrames basálticos.Palavras-chave: resistividade, contaminação.
ABSTRACT. Detecting groundwater in fractured aquifers is always a difficult task. This paper presents the detailed study of a fractured aquifer in Lindóia region, São Paulo, Brazil. The study area was selected after a regional study analyzing the favorability for occurrence of groundwater which classified the area as being of excellent groundwater favorability. The study consisted on fractures mapping based on aerial photographs (scale 1:25,000) and geoelectrical survey (vertical electrical sounding and resistivity imaging). The geophysical data was processed, inverted and analyzed by using geological field data, wells data, springs data and fractures mapped using aerial photographs. The results show that it was possible to define favorable locations for the wells and optimize field work.
ABSTRACT:One key factor for the advance in the study of fluvial deposits is the application of geophysical methods, being the Ground Penetrating Radar one of special value. Although applied to active rivers, the method is not extensively tested on the rock record, bearing interest for hydrocarbon reservoir analogue models. The São Sebastião and Marizal formations were the subject of previous studies, which made possible the comparison of Ground Penetrating Radar survey to previous stratigraphic studies in order to identify the best combination of resolution, penetration and antenna frequency for the studied subject. Eight radar facies were identified, being six of them related to fluvial sedimentary environments, one related to eolian sedimentary environment and one radar facies interpreted as coastal sedimentary environment. The Ground Penetrating Radar data showed compatibility to sedimentary structures in the outcrops, like planar and trough cross-stratified beds. It is noted that the obtained resolution was efficient in the identification of structures up to 0.3 m using a 100 MHz antenna. In this way, the Ground Penetrating Radar survey in outcrops bears great potential for further works on fluvial depositional architecture.KEYWORDS: radar facies; Ground Penetrating Radar; fluvial system; São Sebastião Formation; Marizal Formation.
RESUMO: Um fator-chave para o avanço no estudo de depósitos fluviais é a aplicação de métodos geofísicos, e o Radar de Penetração no Solo é um método de especial valor. Embora amplamente aplicado em ambientes de rios ativos, em ambientes fluviais consolidados esse tipo de estudo é mais escasso, em contrapartida há uma grande importância em mais estudos de modelos análogos de hidrocarboneto. Por essa motivação, o presente trabalho aplicou o Radar de Penetração no Solo em afloramentos já estudados estratigraficamente nas
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